Add Scroll to Top button in Mobile Device

(function ($) {
    var scrollto = $('.jscroll-to-top');

    var do_scroll_to_top = function () {
        var st = $(window).scrollTop();

        if (st > 400) {
            scrollto.addClass('show');
        } else {
            scrollto.removeClass('show');
        }
    }

    scrollto.on('click', function () {
        $('html, body').animate({ scrollTop: 0 }, 600);
        return false;
    });

    $(window).on('scroll load', do_scroll_to_top);
})(jQuery)